The present invention relates generally to material etching, and more particularly to high-rate etching via energy beam dissociation.
Etching is a standard process step used in the fabrication of many of products, most notably semiconductor circuit products for the electronics industry. There are a variety of etching techniques based on the use of either wet chemical etch baths or dry etch plasmas as the etching medium. All of these techniques are characterized by the requirement to initially deposit a mask layer, typically a photoresist layer, over the surface to be etched to thereby define a surface pattern to be etched therein. Such a masking step typically requires the separate steps of depositing the mask layer, properly developing that layer, and after the etching step, removing the mask layer. It would be highly desirable to define the desired etch pattern during the etch step itself, and thereby eliminate the above-described masking steps. However, the etch-rate for such an etch process must be fast enough to provide a clear process advantage over current etch techniques.
In this regard, it is known that a surface may be etched by laser-induced dissociation of a molecule to form a radical etchant adjacent to the surface to be etched. For example, Loper and Tabat, Applied Physics Letters 46(7), Apr. 1, 1985, at page 675, disclose the use of an ArF laser to dissociate COF.sub.2 to obtain fluorine radicals for etching silicon. Likewise, Chuang, Journal of Chemical Physics, 74(2), Jan. 15, 1981, at page 1453, discloses the use of a C0.sub.2 laser to dissociate SF.sub.6 to obtain fluorine radicals for etching silicon. Both of these references describe photo dissociation techniques for generating radical etchants from the interaction of radical precursor molecules with photons at or near a gas-substrate interface. The substrate at the interface undergoes an etching reaction with the radicals in the localized regions exposed to the laser light via the formation of volatile compounds containing the substrate elements. By controlling the localized areas exposed to laser light, it is possible to simultaneously pattern and etch the substrate with submicron resolution. However, radical etching via laser-induced dissociation is slow relative to currently available etching processes.
The invention as claimed is intended to eliminate most presently-required substrate masking steps while providing high-rate radical etching of a material via energy-beam dissociation.